title: Macrophage-derived tumor necrosis factor-alpha is an early component of the molecular cascade leading to angiogenesis in response to aortic injury.
abstract: OBJECTIVE
  The goal of this study was to define the role of tumor necrosis factor-α (TNFα) in the cascade of gene activation that regulates aortic angiogenesis in response to injury.
  
  
  RESULTS
  Angiogenesis was studied by culturing rat or mouse aortic rings in collagen gels. Gene expression was evaluated by quantitative reverse transcription-polymerase chain reaction, microarray analysis, immunocytochemistry, and ELISA. TNFα gene disruption and recombinant TNFα or blocking antibodies against vascular endothelial growth factor (VEGF) or TNF receptors were used to investigate TNFα-mediated angiogenic mechanisms. Resident aortic macrophages were depleted with liposomal clodronate. Angiogenesis was preceded by overexpression of TNFα and TNFα-inducible genes. Studies with isolated cells showed that macrophages were the main source of TNFα. Angiogenesis, VEGF production, and macrophage outgrowth were impaired by TNFα gene disruption and promoted by exogenous TNFα. Antibody-mediated inhibition of TNF receptor 1 significantly inhibited angiogenesis. The proangiogenic effect of TNFα was suppressed by blocking VEGF or by ablating aortic macrophages. Exogenous TNFα, however, maintained a limited proangiogenic capacity in the absence of macrophages and macrophage-mediated VEGF production.
  
  
  CONCLUSIONS
  Overexpression of TNFα is required for optimal VEGF production and angiogenesis in response to injury. This TNFα/VEGF-mediated angiogenic pathway requires macrophages. The residual capacity of TNFα to stimulate angiogenesis in macrophage-depleted aortic cultures implies the existence of a VEGF-independent alternate pathway of TNFα-induced angiogenesis.
authors.affiliation: Pathology and Laboratory Medicine Services, (S-113), Department of Veterans Affairs Puget Sound Health Care System, University of Washington, 1660 S Columbian Way, Seattle, WA 98108, USA.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Ligresti
authors.forename: Alfred C
authors.initials: AC
authors.lastname: Aplin
authors.forename: Penelope
authors.initials: P
authors.lastname: Zorzi
authors.forename: Ann
authors.initials: A
authors.lastname: Morishita
authors.forename: Roberto F
authors.initials: RF
authors.lastname: Nicosia
mesh_terms: D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D001013:Aorta, Thoracic / Q000276:immunology* / Q000293:injuries / Q000503:physiopathology; D015153:Blotting, Western; D002478:Cells, Cultured; D004002:Clodronic Acid / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D020869:Gene Expression Profiling / Q000379:methods; D005786:Gene Expression Regulation; D007150:Immunohistochemistry; D008264:Macrophages / Q000187:drug effects / Q000276:immunology*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D018919:Neovascularization, Physiologic / Q000187:drug effects / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000378:metabolism; D047889:Receptors, Tumor Necrosis Factor, Type II / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D013997:Time Factors; D046509:Tissue Culture Techniques; D014409:Tumor Necrosis Factor-alpha / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism; D057772:Vascular System Injuries / Q000235:genetics / Q000276:immunology* / Q000503:physiopathology
chemical_list: D000906:Antibodies; D012333:RNA, Messenger; D047888:Receptors, Tumor Necrosis Factor, Type I; D047889:Receptors, Tumor Necrosis Factor, Type II; D011994:Recombinant Proteins; C506236:Tnfrsf1a protein, mouse; D014409:Tumor Necrosis Factor-alpha; D042461:Vascular Endothelial Growth Factor A; C467480:vascular endothelial growth factor A, mouse; C467498:vascular endothelial growth factor A, rat; D004002:Clodronic Acid